A proximity photomask exposes a resist-coated surface across a small, controlled gap. It provides the light-blocking pattern while avoiding deliberate physical contact with the resist.
Consider proximity exposure for surfaces that should avoid mask contact, provided the required features can be transferred at the chosen gap and wavelength.
A controlled gap separates the patterned face from the resist. This reduces direct contact, while diffraction across the gap limits how sharply an opening is reproduced. A higher-resolution mask cannot remove the effect of an unsuitable exposure gap.
Substrate material and format, clear and opaque regions, pattern orientation, alignment marks, repeated fields and layer identification can be combined in one mask design.
The product is a patterned glass or fused-silica mask, or an identified set of masks for successive layers. Exposure equipment, photoresist-coated workpieces and the finished devices are separate from the mask itself. Inspection records and packaging form part of the order specification.
| Product configuration | Chrome photomask for exposure across a specified gap |
|---|---|
| Process input | Wavelength, nominal gap and target printed feature |
| Pattern bias | Mask-side bias agreed around gap diffraction and process result |
| Writing reference | Line/space and CD uniformity selected for the mask drawing |
| Acceptance focus | Mask geometry and defects, separated from printed-workpiece results |
Inspect mask features, registration, flatness and chrome defects. Define mask acceptance separately from the customer exposure-process result.
Chrome photomasks for exposure across a controlled gap between the mask and the photoresist-coated workpiece.
Proximity exposure keeps a deliberate separation between the mask and resist-coated surface. Avoiding intended physical contact can help protect sensitive surfaces. The gap also affects diffraction and edge reproduction, so it must be considered with the feature size and exposure optics.
Choose proximity when the substrate arrangement or surface handling favours a gap. Flatness and parallelism influence how consistent that gap remains across the field. A proximity mask does not remove the need to validate the exposure process on the intended resist and workpiece.
Manufacturing capability
Proximity exposure introduces a defined gap between the mask and resist. The written mask geometry, gap, wavelength and target printed feature must be considered together because diffraction across the gap changes the transferred image.
Choose glass or synthetic fused silica around the exposure wavelength, thermal requirements and fixture. State chromium optical density, reflectance, film-side orientation and allowed defect classes. The clear and opaque regions must be unambiguous in the approved artwork.
Quality & Inspection PhotolithographyMasks for a specified exposure gap.
Pattern transfer with the exposure gap defined by the process.
The operating gap changes pattern transfer and surface-contact requirements. The same substrate format can be used, but the process and artwork requirements must be reviewed for that gap.
Proximity photomasks transfer optical patterns across a specified mask-to-workpiece gap.
Define gap, exposure geometry, usable area and smallest line-and-space features together. The fixture must maintain the required relative position.
Working gap, exposure wavelength, artwork, plate thickness, active area and mounting datums.
Also state exposure mode, working gap, viewing direction and substrate outline so the manufacturing data matches the optical arrangement.